1. Field of the Invention
The present invention relates to a method of forming a phosphor film, and more particularly, to a wavelength-convertible light emitting diode (LED) package which adjusts the direction of photons scattered by phosphor particles to improve light extraction efficiency.
2. Description of the Related Art
In general, phosphor for excitation of light is extensively used for converting a peculiar wavelength of light emitted from a light source such as a light emitting diode (LED) to a wavelength of other desired color of light. In order to manufacture such an LED package capable of converting the wavelength, for example, a resin part with phosphor dispersed therein can be formed to encapsulate an LED chip or a phosphor film can be formed on a surface of an LED chip.
In case of an LED package adopting a resin part with phosphor dispersed therein, excitation-wavelength light passes through the phosphors in the resin part numerous times, thus leading to low efficiency due to the refraction and reflection by the phosphor. In comparison, in case of an LED package with a phosphor film directly formed on a surface of the chip, excitation-wavelength light is directly absorbed in the phosphor, which can advantageously mitigate degradation of efficiency due to the reflection or refraction by the phosphor.
However, even the structure with the phosphor film formed on the surface of the chip does not ensure effective light paths because of the dense structure of the phosphor film. Also, some portion of light reflected by the phosphor particles may be absorbed back into the LED chip, degrading light efficiency.